1. Technical Field
The present disclosure generally relates to electrosurgery. More particularly, the present disclosure relates to systems and methods for compensating for losses to obtain accurate electrical measurements in cordless or fixed-reactance cabled electrosurgical systems.
2. Background of Related Art
Electrosurgery involves the application of high-frequency electric current to cut or modify biological tissue during a surgical procedure. Electrosurgery is performed using an electrosurgical generator, an active electrode, and a return electrode. The electrosurgical generator (also referred to as a power supply or waveform generator) generates an alternating current (AC), which is applied to a patient's tissue through the active electrode and is returned to the electrosurgical generator through the return electrode. The alternating current typically has a frequency above 100 kilohertz to avoid muscle and/or nerve stimulation.
During electrosurgery, the alternating current generated by the electrosurgical generator is conducted through tissue disposed between the active and return electrodes. The tissue's impedance converts the electrical energy (also referred to as electrosurgical energy) associated with the alternating current into heat, which causes the tissue temperature to rise. The electrosurgical generator controls the heating of the tissue, by controlling the electric power (i.e., electrical energy per time) provided to the tissue. Although many other variables affect the total heating of the tissue, increased current density usually leads to increased heating. The electrosurgical energy is typically used for cutting, dissecting, ablating, coagulating, and/or sealing tissue.
An electrosurgical generator includes a controller that controls the power applied to the tissue over some time period. The power applied to the tissue is controlled based upon power measurements and a power level set by the user or a power level needed to achieve a desired tissue effect. The power measurements are obtained by measuring the voltage and current of the RF signal generated by the RF output stage of the electrosurgical generator and calculating power based upon the measured voltage and current.
The voltage and current measured by the sensors of the electrosurgical generator, however, may not equal the actual voltage and current applied to the tissue because of RF impedance losses in the transmission line connecting the RF output stage of the electrosurgical generator to the electrodes of the electrosurgical instrument. As a result, the power calculations may be inaccurate and may lead to improper control of the electrosurgical energy applied to the tissue.
The affect of the RF impedance losses on the power and impedance calculations may be reduced by more accurately sampling the phase between the voltage and the current. However, this method requires greater computational complexity and more expensive high-speed hardware.